TweetFollow Us on Twitter

Serious Wireless

Volume Number: 19 (2003)
Issue Number: 4
Column Tag: Wireless Networking

Serious Wireless

Looking to get Point-to-Point Wireless between locations? Here's a truly robust solution.

by Neil Ticktin

Why The Change?

Some of you may recall my first wireless article a few years back (MacTech Magazine, January 2000 issue, "Going Wireless!" <http://www.mactech.com/articles/mactech/Vol.16/16.01/GoingWireless/>). In that article, I wanted to implement a reliable wireless link between my house, and the office. I specifically wanted to do anything and everything that I could to avoid the phone company for my net connection. Wireless gave me the ability to get high quality, reliable access that was completely within my control, and without any monthly fees. Sounded good to me!

And it was great. For years, I reliably had a 1.4 mbps connection between my house and my office ... a drive of about 2.5 miles, and about 1.5 miles as the bird flies. I was able to do it with off the shelf materials ... Lucent boxes (very similar technology to what's in the original Airport Base Stations, but with Lucent software to glue it all together).

The problem is, 1.4 mbps is not what it was 3+ years ago. More importantly, even though I was physically fairly close to the office, I was suffering latencies in the 30-millisecond range. Now while that's not a problem for things like web browsing, certain functions like access to our FileMaker Server were way too slow for me to use the way I wanted to.

You see, some applications move a lot of very small pieces of data around. The theory we had with our FileMaker sluggishness is that the latency was too great (especially compared to the LAN at the office), and essentially, it was causing the network to "thrash" when certain functions performed. As we saw in installing the new setup, reducing latency made a huge difference in the way these systems worked.

By the way, in case you were thinking about utilizing the new 802.11g standard at 54 mbps, beware of something. 802.11g is great for indoor LANs, but the standard is still in flux, and more importantly, the amount of distance you can get (at least inside) is about 1/3 of what is available with 802.11b. So far, I've not heard of anyone using 802.11b for outdoor point-to-point access.

The New Plan

You may remember from the previous article that I don't have line of sight from my house to the office. The solution? I knocked on the door of a neighbor up on the hill and offered him a great Internet connection in exchange for having some equipment on his roof. As you might well imagine, that's a deal that works out well for all. So, unlike many installations, I actually have a point to point-to-point connection between my house and the office. In other words, my connection goes from my house to David's house, to the office ... point to point to point.

What I needed to do now is find new equipment that could reduce the latency, as well as increase the bandwidth. I turned to my friends over at Westlink Wireless http://www.westlinkwireless.com. Eddie West helped me to take a look at the problem and recommended that we look at some of the proprietary radios out there.

The Radios

We selected the Trango Broadband radios <http://www.trangobroadband.com>. Specifically, the Access5800 Wireless Broadband Access Solution. Specifically, we're using a combination of their "Access Points" (AP) and their "Subscriber Units" (SU). The APs are typically located at the center of a network, or head-end of a wireless point of presence, and they communicate with one or more SUs. You can have up to 500 SUs per AP unit. We're using the Access Point, M5800S-AP-60, $895; and a 3 Mile Subscriber Unit, M5800S-SU, $495. (There's also a 10-mile Subscriber Unit, which has a DirecTV style dish on it.)

Radios have a certain amount of range where the signal is "visible". In Trango's terms, their AP units have a 60-degree sector. Because my house and my office are not within the same sector of visibility (they are on opposite sides of David's house), I need to have to Access Points each talking to a Subscriber Unit (4 radios in all). Put another way, the AP at my house talks to a SU at David's which is connected through a small Ethernet switch to an AP at David's which talks to an SU at my office.

The radios, and antennae are all combined into a single, weatherproof unit. No power is necessary on the roof, only at the power injector, which is likely near your router or switch. The units use a "power injector" over Ethernet. The radio can be 100 meters from the power injector. The injector has three connections -- a power cable, and two Ethernet ports (one to your LAN and one to the radio). For some installations, not having power at the radio is critical ... and it's almost always handy.


Figure 1. Access Point (the 3 mile Subscriber Unit)


Figure 2. Antenna for 10 mile Subscriber Unit Configuration

Radio Tech Stuff

These Trango radios are pretty cool. A specific benefit to us is that they are not based on one of the 802.11 standards, and are therefore they were able to do some special things, are high performance and secure. Specifically, they are based on Direct Sequence Spread Spectrum technology that operates in the ISM 5.7 - 5.8 GHz range. They theoretically deliver up to 10 Mbps user throughput reliably. An Access Point can be up to 20 miles from the SU, and supports QoS and have on the fly bandwidth throttling. Spread spectrum has the inherent advantage over other forms of transmission in that it can still recover data even in the most noisy of RF environments where other architectures fail. This isn't something new, just something very reliable and robust.

Using a proprietary protocol called SMARTPolling, the Trango radios are able to discover one another, as well deliver bandwidth more efficiently. And, if you are concerned with balancing the signal between SUs at different distances, the APs have a "power leveling" feature. As part of the "power on" sequence, the AP determines how far away a given SU is, and actively diminishes or increases its output power to ensure a quality of service.

To keep usage under control, you can optimize the Committed Information Rate / Maximum Information Rate (CIR/MIR) and provide bandwidth management/throttling per individual SU.

One of the more interesting features is the Dynamic RF Packet Sizing allows the radios to optimize data bandwidth utilization with maximum RF sensitivity. Unlike other solutions which use fixed RF packet sizes, the Access5800's protocol dynamically analyzes each Ethernet packet and transmits at an optimal length, 64 bytes (in the case of URL requests) to 1600 bytes.

SU's can be remotely managed through the AP using a host of commands or via HTTP web interface, telnet, or serial interface. The radios have a built in RSSI LED and RSSI Telnet Command for SU antenna alignment.

And, there's a fallback channel provision on the SU which offers built in redundancy. In the event an SU cannot communicate with its primary AP, the SU will intelligently search for a pre-programmed fall back AP to communicate with. This feature allows the network operator to actually sleep at night knowing that each user's network link will still be up in the morning.

But there are two features that are super cool, especially if you are familiar with installing wireless networks. First, there are internal dual polarized antennas that are software switchable -- yes, you can change the polarity through the software interface! Second, the radios have built in site survey tools that allow you to check for interference (see Listing 1).

Listing 1: Site Survey Results

ss> survey 3 v
Running site survey for 30 secs.
Press [space] then [enter] to stop
Vertical Polarization        Channel is clear if avg & max < -92dBm
freq   max    avg               freq   max    avg
Mhz    dBm    dBm    clear      Mhz    dBm    dBm    clear
5724   -87    -97     *no*      5788   -93    -99     yes 
5728   -81    -95     *no*      5792   -93    -99     yes 
5732   -80    -95     *no*      5796   -93    -99     yes 
5736   -79    -95     *no*      5800   -93    -99     yes 
5740   -79    -95     *no*      5804   -89    -99     *no*
5744   -80    -93     *no*      5808   -88    -97     *no*
5748   -82    -97     *no*      5812   -82    -97     *no*
5752   -91    -99     *no*      5816   -81    -95     *no*
5756   -93    -99     yes       5820   -80    -91     *no*
5760   -93    -99     yes       5824   -65    -80     *no*
5764   -93    -99     yes       5828   -57    -77     *no*
5768   -93    -99     yes       5832   -57    -85     *no*
5772   -93    -99     yes       5836   -57    -83     *no*
5776   -93    -99     yes       5840   -57    -83     *no*
5780   -93    -99     yes       5844   -59    -85     *no*
5784   -93    -99     yes       5848   -63    -79     *no*

Security

With all the talk about security over Wi-Fi, you may be concerned about the security offered by a wireless solution like this. I'm not. First, because these radios are proprietary, it will take a lot more effort for someone to figure them out. Second, the radios will only talk to another radio that it knows the hardware (aka MAC) address of. Third, Trango has built these radios with security in mind. I have a lot greater concerns about other attacks on our network than I do about someone entering in through this wireless entry point.

AppleTalk

If you are still using AppleTalk protocols in your network, no worries. These radios can handle them. Since AppleTalk uses AARP, you will need to turn the multicast packet switch to off (disabled). Once you do that, AppleTalk Phase 1 and 2 pass traffic with no problems. It's pretty cool to pull up a zone at my house from the office ... in fact, I have a Home Automation server at the house that stores my MP3s, and I play them in iTunes over File Sharing on a machine in my office.

Broadcasting Changes

One of the cool things about these radios is that you can have the Access Point broadcast changes to the APs. This is, obviously, especially useful if you have many SUs talking to the AP ... and again, shows the heritage of this radio being targeted for ISPs.

What's an Install Like?

These radios are intended for ISPs looking to deploy in their network. On one hand, that's great because that market won't tolerate a lot of problems ... the radios need to be robust. The flip side to this is that this is not a product that is currently being marketed to the end user. In part, that's because you should have some expertise when deploying it.

Unless you are an expert yourself, you should talk to someone who is. Our experience with Westlink Wireless showed the importance of this. Eddie's ability to size up the network environment and to work out the kinks was important to our install (mostly because we were doing point to point to point instead of point to point as most people would.) For example, I never would have known that it was better to have an AP and SU at David's instead of two AP's.

You need to make sure of several things. First, do you have radio line of sight? From my previous article, radio line of sight takes into account the shape of the zone that the radio waves travel in. This is called the "Freznel" zone. Basically, the radio waves travel between the antennas covering an area that is shaped long an elongated football. In other words, the clearance that you need halfway between the antennas is greater than right at each antenna. In many cases, this means that you are at an advantage if one of the antennae locations is at a higher elevation than the other.

You also need to make sure that you aren't trying to send the signal through or near items that could cause interference. For example, the metal flashings around the top of a chimney might be a problem if you are mounting the radio to a chimney. Or, if you were thinking that you could should the signal through foliage, some may be more tolerant than others. (I learned the hard way that pine trees are really tough to deal with and should always be avoided.)

My recommendation? Either plan for a bunch experimentation and learning, or better yet, buy the radio through a reseller like Westlink Wireless so that you have somewhere to consult if you run into issues.

The Interface

One of the things that I didn't like about the Lucent solution that I had was that it required that I talk to it through a piece of Windows software. VirtualPC, as always, came to the rescue so that I could use my Mac to configure the radios ... and VirtualPC 6 is better than ever in this way.

The Trango radios, though, can be configured not only through a web interface, but also via telnet. A quick overview of the command set gives you an idea of all that you can do with this interface.

Listing 2: Telnet interface for Trango Access Point

* ALL
? [command]                                         !
cd [..|main|net|rf|fw|ss]                           date
date <month> <day> <year>         help [command]
logout                                              opmode [ap]
reboot                                              restart
sysinfo                                             systemsetting <backup|restore>
sw [<sw #> <on|off>]                    time
time <hour> <min> <sec>
updateflash 
<mainimage|fpgaimage|sumainimage|sufpgaimage|systemsetting|sudb>

* MAIN
bcastscant <all|suid> <ch#> <h|v> [<ch#> <h|v> ...
bcastsuimage <all|suid> <regular|fast> <target hw_ver>
bcastsuimage [stop]                                 password
_password <new password> <new password>
set suid <id>                                 set apid <id>
set baseid <id>                               set ip <ip addr>
set defaultopmode [ap|su] <min,0..60>
set defaultopmode off                               set mir [on|off]
set mir threshold <kbps>
set rssitarget <threshold> <fade margin>
su <suid> [nonstop]                           su all [nonstop]
su changechannel <all|suid> <ch#> <h|v>  su [live|poweroff|priority]
su <ping|info|status> <suid>            su reboot <all|suid>
su restart <all|suid>                         su testrflink <all|suid> [r]
su powerleveling <all|suid> [target dB]
su sw <suid> <sw #> <on|off>      sudb [dload | view]
sudb add <suid> <pr|reg> <cir,kbps> <mir,kbps> <device id,hex>
sudb delete <suid>                            sudb modify <suid> <cir|mir> <kbps>
sudb modify <suid> <su2su> <group id,hex>
sudb view
* NET
ping <ip addr>                                tftpd [on|off]
* RF
cf2cf ap [default|<size>]                     freq scantable
freq channeltable                                   freq writescan [<ch#> <h|v>] ...
freq writechannel [<ch#> <freq>] ...
freq <ch #> <h|v>                       polar <h|v>
power set <dBm>                               power table
rfreport [reset]                                    rfrxthreshold <off|-80|-75|-70 |-65>
rfrxthreshold table
* FW
mainupdate                                          fpgaupdate
* SS
survey <time, sec> <h|v>                rssi <ch #> <h|v>
apsearch <secs> <ch#> <h|v> [<ch#> <h|v>]...

The Good, The Bad, and the Ugly

In general, I love these Trango products. You can't believe how useful it is to change polarity of antennae in software ... or to do a site survey from a telnet interface. More importantly, these are robust radios that are serious business, and I'm thrilled to have them in my network.

There are a couple of things that got to me on these radios, and are worthy of mention here. First, and these are minor, the RJ-45 jack on the power injector is backwards. The clip is against the wall, and it can be very difficult to pull the cord out without having a small flathead screwdriver. Also, the arm that the radio mounts on could be easier to articulate, but it's not bad.

The one thing that I truly despise in these radios is what I can best describe as an over the top security feature. Once set up, you can really only configure these units from one side of the connection because it limits where you can log in from. Remember, these things were designed for ISPs who deploy one or more APs and then have tons of SUs. The idea is that you wouldn't' want a customer to be able to telnet into a SU, so everything needs to happen from the head end side of things. Now, it is possible to log in from the SU side, but you have to do so within the first 30 or so seconds from when it's been power cycled. This is quite the pain and for me, almost useless as I want to manage things remotely, not on site. I have no problem with this feature being available as a software switch, but even if I was an ISP, I wouldn't want this feature turned on by default -- I want to be able to configure these things from both sides! And, this one sided nature doesn't stop there, you can't even ping the radio from the client side. This means that an ISP can't even ask their customer if they can ping a radio when the connection is down! What a pain for those in tech support who have chased problems only to find that the client unplugged a cable somewhere. Unfortunately, because it would take a complete rewrite to fix, I don't expect this feature to go away soon.

Another limitation is their use of "opmodes". Radios are usually configured when they are not running in either the Access Point or Subscriber Unit "opmode". Disable the opmode, and you disable the link. Enable the opmode, and you can't configure the unit. This is different from other types of radios that seem to be able to do both.

What's Coming

There are some new things coming down the pike on these radios. A new firmware upgrade will have SNMP capability (this will be a free upgrade). And, there's a dual-band version (5.3/5.8 GHz) coming soon too. Lastly, expected in May 2003, there will be a true point-to-point version of the radios, which may interest many of you.

The End Result

Proof is in the pudding, right?

These radios are fast ... I'm seeing communications at under 300 microseconds (not milliseconds) between the radios. But, a radio ping is different from an IP ping which is what we really care about.

In my point to point to point setup, I came from my older set up doing 1.4 mpbs with 30 millisecond latency to a new set up of 6-8 mbps (depends on the direction) with 5 milliseconds latency. The speed is so different and so much better that, using Retrospect Server, I'm actually now running backups of my home computers to tape drives at the office.

Doesn't get much better than that.


Neil is the publisher of MacTech Magazine. As a closet geek, he tends to experiment with some of the more interesting forms of technology, and then frightening the magazine staff by announcing he'll write about them. You can reach him at publisher@mactech.com

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Dashlane 6.2027.0 - Password manager and...
Dashlane is an award-winning service that revolutionizes the online experience by replacing the drudgery of everyday transactional processes with convenient, automated simplicity - in other words,... Read more
ffWorks 2.1.5 - Convert multimedia files...
ffWorks, focused on simplicity, brings a fresh approach to the use of FFmpeg, allowing you to create ultra-high-quality movies without the need to write a single line of code on the command-line.... Read more
Dropbox 101.4.434 - Cloud backup and syn...
Dropbox for Mac is a file hosting service that provides cloud storage, file synchronization, personal cloud, and client software. It is a modern workspace that allows you to get to all of your files... Read more
1Password 7.6 - Powerful password manage...
1Password is a password manager that uniquely brings you both security and convenience. It is the only program that provides anti-phishing protection and goes beyond password management by adding Web... Read more
EyeTV 4.0.0 - Watch and record TV on you...
EyeTV brings a rich TV experience to your Mac. Watch live TV on your Mac. Pause, rewind, and record whenever you want. EyeTV gives you powerful control over what you watch and how you watch it. Put... Read more
Tidy Up 5.3.7 - Find duplicate files and...
Tidy Up is a full-featured duplicate finder and disk-tidiness utility. Features: Supports Lightroom: it is now possible to search and collect duplicates directly in the Lightroom library. Multiple... Read more
Pinegrow 5.97 - Mockup and design web pa...
Pinegrow (was Pinegrow Web Designer) is desktop app that lets you mockup and design webpages faster with multi-page editing, CSS and LESS styling, and smart components for Bootstrap, Foundation,... Read more
BlueStacks 4.210.0 - Run Android applica...
BlueStacks App Player lets you run your Android apps fast and fullscreen on your Mac. Feature comparison chart How to install Bluestacks on your Mac Go to MacUpdate and click the green "Download"... Read more
WhatsApp 2.2027.10 - Desktop client for...
WhatsApp is the desktop client for WhatsApp Messenger, a cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS. WhatsApp Messenger is available for... Read more
Art Text 4.0.1 - $29.99
Art Text is graphic design software specifically tuned for lettering, typography, text mockups and various artistic text effects. Supplied with a great variety of ready to use styles and materials,... Read more

Latest Forum Discussions

See All

Clash Royale: The Road to Legendary Aren...
Supercell recently celebrated its 10th anniversary and their best title, Clash Royale, is as good as it's ever been. Even for lapsed players, returning to the game is as easy as can be. If you want to join us in picking the game back up, we've put... | Read more »
Steam Link Spotlight - Disco Elysium
Steam Link Spotlight is a feature where we look at PC games that play exceptionally well using the Steam Link app. Our last entry was Signs of the Sojourner Read about how it plays using Steam Link over here. | Read more »
Distract Yourself With These Great Mobil...
There’s a lot going on right now, and I don’t really feel like trying to write some kind of pithy intro for it. All I’ll say is lots of people have been coming together and helping each other in small ways, and I’m choosing to focus on that as I... | Read more »
Pokemon Go's July Community Day wil...
Pokemon Go developers have announced the details concerning the upcoming Gastly Community Day. This particular event was selected by the players of the game after the Gas Pokemon came in second place after a poll that decided which Pokemon would... | Read more »
Clash Royale: The Road to Legendary Aren...
Supercell recently celebrated its 10th anniversary and their best title, Clash Royale, is as good as it's ever been. Even for lapsed players, returning to the game is as easy as can be. If you want to join us in picking the game back up, we've put... | Read more »
Detective Di is a point-and-click murder...
Detective Di is a point-and-click murder mystery set in Tang Dynasty-era China. You'll take on the role of China's best-known investigator, Di Renjie, as he solves a series of grisly murders that will ultimately lead him on a collision course with... | Read more »
Dissidia Final Fantasy Opera Omnia is se...
Dissidia Final Fantasy Opera Omnia, one of Square Enix's many popular mobile RPGs, has announced a plethora of in-game events that are set to take place over the summer. This will include several rewards, Free Multi Draws and more. [Read more] | Read more »
Sphaze is a neat-looking puzzler where y...
Sphaze is a neat-looking puzzler where you'll work to guide robots through increasingly elaborate mazes. It's set in a visually distinct world that's equal parts fantasy and sci-fi, and it's finally launched today for iOS and Android devices. [... | Read more »
Apple Arcade is in trouble
Yesterday, Bloomberg reported that Apple is disappointed in the performance of Apple Arcade and will be shifting their approach to the service by focusing on games that can retain subscribers and canceling other upcoming releases that don't fit... | Read more »
Pixel Petz, an inventive platform for de...
Pixel Petz has built up a sizeable player base thanks to its layered, easy-to-understand creative tools and friendly social experience. It revolves around designing, trading, and playing with a unique collection of pixel art pets, and it's out now... | Read more »

Price Scanner via MacPrices.net

B&H Photo offers $200-$300 discounts on A...
B&H Photo has new 16″ MacBook Pros on sale today for $200-$300 off Apple’s MSRP, starting at $2149. Expedited shipping is free to many addresses in the US: – 2019 16″ 2.6GHz 6-Core MacBook Pro... Read more
Clearance 2019 15″ MacBook Pros on sale today...
Amazon-owned Woot is blowing out Apple refurbished, clearance 2019 15″ MacBook Pros starting at only $1579 and up to $950 off Apple’s original MSRP. According to Woot, “These MacBooks are Refurbished... Read more
Apple Refurbished iMac Pros available for $35...
Amazon-owned Woot is selling Apple refurbished 27″ 3.2GHz 8-Core iMac Pros for $3599.99 shipped. That’s $1400 off Apple’s original MSRP for this model. According to Woot, these iMac Pros are “Factory... Read more
Clearance 2019 13″ 2.4GHz/256GB MacBook Pro o...
B&H Photo has dropped their price on the clearance 2019 13″ 2.4GHz/256GB Quad-Core Silver MacBook Pro by $500 off Apple’s original MSRP to a new low of only $1299. Expedited shipping is free to... Read more
$219 Apple AirPods Pro are back at Verizon, s...
Verizon has Apple AirPods Pro on sale again for a limited time for $219.99 on their online store. Their price is $30 off Apple’s MSRP, and it’s the lowest price we’ve seen for AirPods Pro. Available... Read more
Apple’s $779 13″ MacBook Air deal returns to...
Apple has clearance, Certified Refurbished, 2019 13″ MacBook Airs available again starting at $779. Each MacBook features a new outer case, comes with a standard Apple one-year warranty, and is... Read more
$200 13″ MacBook Pro discounts are back at Am...
Amazon has 2020 13″ 2.0GHz MacBook Pros on sale again today for $150-$200 off Apple’s MSRP. Shipping is free. Be sure to purchase the MacBook Pro from Amazon, rather than a third-party seller, and... Read more
Deal Alert! Apple AirPods with Wireless Charg...
Sams Club has Apple AirPods with Wireless Charging Case on sale on their online store for only $149.98 from July 6, 2020 to July 9, 2020. Their price is $50 off Apple’s MSRP, and it’s the lowest... Read more
Xfinity Mobile promo: Apple iPhone XS models...
Take $300 off the purchase of any Apple iPhone XS model at Xfinity Mobile while supplies last. Service plan required: – 64GB iPhone XS: $599.99 save $300 – 256GB iPhone XS: $749.99 save $300 – 512GB... Read more
New July 2020 promo at US Cellular: Switch an...
US Cellular has introduced a new July 2020 deal offering free 64GB Apple iPhone 11 smartphones to customers opening a new line of service. No trade-in required, and discounts are applied via monthly... Read more

Jobs Board

Product Manager, *Apple* Commercial Sales -...
Product Manager, Apple Commercial Sales Austin, TX, US Requisition Number:77652 As an Apple Product Manager for the Commercial Sales team at Insight, you Read more
Physical Therapist Assistant - *Apple* Hill...
Physical Therapist Assistant - Apple Hill Rehab - Full Time Tracking Code 62519 Job Description General Summary: Under the direct supervision of a licensed Physical Read more
Operating Room Assistant, *Apple* Hill Surg...
Operating Room Assistant, Apple Hill Surgical Center - Full Time, Day Shift, Monday - Saturday availability required Tracking Code 62363 Job Description Operating Read more
Perioperative RN - ( *Apple* Hill Surgical C...
Perioperative RN - ( Apple Hill Surgical Center) Tracking Code 60593 Job Description Monday - Friday - Full Time Days Possible Saturdays General Summary: Under the Read more
Product Manager, *Apple* Commercial Sales -...
Product Manager, Apple Commercial Sales Austin, TX, US Requisition Number:77652 As an Apple Product Manager for the Commercial Sales team at Insight, you Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.